The goal of this proposal is to continue to assess the impact of new vaccines and vaccine policies on disease prevention through the Enhanced Surveillance for New Vaccine Preventable Diseases cooperative agreement. Our specific aims include: 1) conducting active population-based surveillance for vaccine preventable diseases throughout the Nashville/Davidson County population and performing epidemiologic and health services research on vaccine impact by utilizing the Tennessee Medicaid database;2) assessing issues related to provider implementation of new vaccine recommendations;and 3) enhancing inpatient and outpatient surveillance of children with fever and/or acute respiratory disease in Davidson County. A particular focus of our work during the upcoming funding period will be on influenza. With the new recommendation of routine influenza vaccination for children ages 6 -23 months, an immunization survey will be conducted in area practices to determine the influenza vaccine coverage rate for healthy children ages 6- 23 months, as well as older children with high-risk medical conditions in a representative sample of County children. In addition, surveys of primary care providers will help determine provider and practice characteristics that influence adoption of these new vaccine recommendations. Influenza vaccine effectiveness will evaluated for the 2003-2004 and 2004-2005 influenza seasons using a case cohort design. Exposure to influenza vaccine will use data obtained from the outpatient practice survey. Cases will be identified with augmented inpatient surveillance which will attempt to enroll all County children aged <5 years hospitalized with influenza 6 days/week as well as a representative sample of children seen only in the emergency room for influenza. These data will be instrumental in assessingthe impact of the new influenza vaccination recommendations. The utility of this network in evaluating new vaccines and vaccine policies is great.